THE HAGUE, May 2 (Xinhua) -- The chief prosecutor of the International Tribunal for the Former Yugoslavia, Serge Brammertz, said on Wednesday he was satisfied with the swift pre-trails of accused war criminals Ratko Mladic and Goran Hadzic, but warned lots of work remained to be done.

Former Bosnian Serb army commander Mladic's trail will start on May 16, less than a year after was arrested on May 26, 2011.

"All parties have done their homework if I may say so," the chief prosecutor told Xinhua after a meeting with foreign correspondents in The Hague.

"We, as an office of the prosecutor, presented an amended indictment very soon after the arrest. In other cases, it took longer to have an amended indictment presented, Brammertz said, adding it was up to the trial judges to determine the dynamic of the trial.

The prosecution intends to bring in 411 witnesses in the trial against Mladic and has 200 hours to present its case before the judge. In the case of former Bosnian Serb politician Radovan Karadzic, in which the prosecution is due to finish arguments this month, the prosecution was allowed 300 hours and used 290 hours.

"We have reduced the number of incidents we have to prove in court," Brammertz said. "We have 11 counts related to the ethnic cleansing in a number of municipalities in Bosnia between 1992 and 1995. We will present evidence in relation to the three years of siege of Sarajevo, evidence in relation to the genocide in Srebrenica."

Goran Hadzic, former president of the Republic of Serbian Krajina, was the last of 161 indicted fugitives to be arrested in July 2011. His trial will start in mid-October, when Karadzic begins to present his defence.

Stating that while they were were pleased Mladic and Karadzic were arrested, Brammertz called for more cooperation from Serbian authorities.

"We want to know how it was possible they could hide for so many years in Serbia without being arrested. We have requested the Serbian authorities to provide us with as much information from their internal investigations into the possible supporters of the fugitives' networks. We are not yet satisfied with the information we received," he said.

The United Nations Security Council called on the tribunal to finish its work by 31 December, 2014, and transfer its remaining responsibilities to the International Residual Mechanism for Criminal Tribunals which will take over from the former Yugoslavia tribunal on July 1, 2013.

"I think all people at the tribunal are committed to meet the deadline," Brammertz said. "It needs to be seen if perhaps additional time will be needed to finish all appeals, but it's too early to say."